1. Field of the Invention
Embodiments of the invention relate to a display device, and more particularly, to an organic electroluminescence display device. Although embodiments of the invention are suitable for a wide scope of applications, they are particularly suitable for supplying low current to an organic light emitting device (OLED) even in the case of a high data current being applied to the an organic light emitting device.
2. Description of the Related Art
Recently, organic electroluminescence display (OLED) devices have attracted considerable attention as a display device of the next generation due to its advantages of high contrast ratio, high luminance, low power consumption, fast response time, and wide viewing angle. Because of such advantages, the organic electroluminescence display device is widely used for mobile phones, personal digital assistants, computers, and televisions. Furthermore, the organic electroluminescence display device is a self-light emitting type, thereby displaying visible light including blue light. Accordingly, the OLED device can display colors close to natural colors. Moreover, since the organic electroluminescence display device has fast response time of several microseconds, the organic electroluminescence display device can easily display moving images. Further, the organic electroluminescence display device has no limitation on viewing angle and is stable at low temperatures. Furthermore, the organic electroluminescence display device can be fabricated through a simple thin film fabrication process since the organic electroluminescence display device is an ultra-thin film type display device.
The organic electroluminescence display device displays images by driving pixels of M×N organic electroluminescence display devices using a voltage or current. A driven pixel emits light by electrically exciting a fluorescent organic compound. However, the organic electroluminescence display device has problems in that luminance is irregular and driving control becomes difficult due to sensitivity differences among blue, green and red fluorescent organic compounds if a voltage driving mode is applied to the organic electroluminescence display device in the same manner as a liquid crystal display device. Accordingly, a current driving mode is typically used in the driving of organic electroluminescence display devices.
An active matrix type organic electroluminescence display device is widely used, wherein a plurality of pixels are arranged in a matrix arrangement and image information is selectively supplied to each pixel through a switching device, such as a thin film transistor provided in each pixel. However, in a current driving mode, which drives a plurality of organic light emitting diodes (OLED) of the organic electroluminescence display devices using a current, a parasitic capacitance exists between a data line supplying a data current to a data signal and a cathode of the OLED. In this case, the capacitance occurring in the data line should be charged quickly to drive the organic electroluminescence display device at a high speed. However, problems occur in that a high current is required to quickly charge the capacitance of the data line, and the OLED is damaged if the high current flows in the OLED. In other words, the related art current driving mode has a problem in that the OLED to which the high current is supplied should be driven at a low current but yet high speeds are desired.